THE LACTOCOCCUS LACTIS CodY REGULON: IDENTIFICATION OF A

CONSERVED cis-REGULATORY ELEMENT Chris D. den Hengst

1, Sacha A. F. T. van Hijum

1, Jan M. W. Geurts

2, Arjen Nauta

2, Jan

Kok1 and Oscar P. Kuipers

1

From the1Department of Genetics, Groningen Biomolecular Sciences and Biotechnology

Institute, Kerklaan 30, 9751 NN Haren, The Netherlands, and 2Friesland Foods Corporate

Research, P.O. Box 87, 7400 AB Deventer, The NetherlandsRunning title: Global regulation by CodY

Address correspondence to: Oscar P. Kuipers, Department of Genetics, Groningen Biomolecular Sciences and Biotechnology Institute, Kerklaan 30, 9751 NN Haren Tel. +31 50 363 2093; Fax +31 50 363 2348; E-mail O.P.Kuipers@rug.nl

CodY of Lactococcus lactis MG1363 is a

transcriptional regulator that represses the

expression of several genes encoding proteins of

the proteolytic system. DNA microarray

analysis, comparing the expression profiles of

L. lactis MG1363 and an isogenic strain in

which codY was mutated, was used to

determine the CodY regulon. In peptide-rich

medium and exponentially growing cells, where

CodY exerts strong repressing activity, the

expression of over 30 genes was significantly

increased upon removal of codY. The

differentially expressed genes included those

predominantly involved in amino acid

transport and metabolism. In addition, several

genes belonging to other functional categories

were derepressed, stressing the pleiotropic role

of CodY. Scrutinizing the transcriptome data

with bioinformatics tools revealed the presence

of a novel overrepresented motif in the

upstream regions of several of the genes

derepressed in L. lactis MG1363 codY.

Evidence is presented that this 15-bps cis-

sequence, AATTTTCWGAAAATT, serves as a

high-affinity binding site for CodY, as shown

by electrophoretic mobility shift assays and

DNaseI footprinting analyses. The presence of

this CodY-box is sufficient to evoke CodY-

mediated regulation in vivo. A copy of this

motif is also present in the upstream region of

codY itself. It is shown that CodY regulates its

own synthesis and requires the CodY-box and

branched-chain amino acids to interact with its

promoter.

For the Gram-positive organism L. lactis,a lactic acid bacterium (LAB) auxotrophic for branched-chain amino acids (BCAAs), methionine

and histidine (1-3), maintenance of the nitrogen balance is essential. When this bacterium grows in milk, it uses the ubiquitous milk proteins (caseins) for its growth, employing a comprehensive and balanced proteolytic system (4-6). The extracellular cell wall-bound serine proteinase (PrtP) is an essential part of the proteolytic system, as it hydrolyses the large caseins into smaller fragments. These peptides of various sizes, and free amino acids, can then be taken up into the cell by various transport systems, e.g. the oligopeptide transport system Opp (4) and the di- and tripeptide transport systems DtpP and DtpT (7,8). Once inside, the peptides are degraded further by either endopeptidases (e.g. PepO and PepF) or aminopeptidases (e.g. PepN, PepX and PepC) (9).

Although the proteolytic system of LAB has been characterized thoroughly over the past 20 years (6), new components are still being identified. For example, upon deletion the main transport system for oligopeptides (opp), growth on media containing specific oligopeptides was still possible (10), suggesting the presence of at least one additional peptide transport system. Recently, a novel peptide transporter has been identified, encoded by dpp (opt), which is able to take over (part of) the role of opp (10-12).

Previous studies have shown that expression in L. lactis MG1363 of a number of genes of the proteolytic system is repressed in nitrogen-rich media. When L. lactis encounters limiting amounts of nitrogen, repression is relieved (13,14). From recent studies it has become apparent that the transcriptional regulator CodY is responsible for repression of the genes prtP/prtM, opp, pepN, pepC, araT and bcaT in response to nitrogen availability (14-17). More recently, it has been established that the nitrogen

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signal that affects the strength of repression by CodY consists of BCAAs. For both L. lactis and Bacillus subtilis it has been shown that these amino acids act as cofactors that directly stimulate CodY binding to regulatory sites of its target genes (17-19). An additional factor modulating the activity of CodY was identified in B. subtilis. In this organism, GTP, a marker of the energy state of the cell, can stimulate CodY binding by a mechanism independent of BCAAs. Such a mechanism seems to be absent in L. lactis (17,18). Complex modulation of CodY activity in B. subtilis is probably required, as CodY exerts its effects on a wide variety of genes, among which several that are not involved in nitrogen metabolism (20). CodY was first identified in this organism, where it serves as a nutritional repressor of the dipeptide-permease operon (21,22), and of genes involved in amino acid metabolism (19,23-28), carbon and energy metabolism (29), motility (30), antibiotics production (31) and competence development (20,32).

In spite of the detailed studies in B. subtilis and L. lactis on CodY-mediated regulation, which revealed direct interaction between CodY and the regulatory regions of its targets by means of in vitro DNA binding assays (17), no CodY-recognition sequence could be deduced. Moreover, a genome-wide in vivoscreening for CodY-DNA interaction sites in B. subtilis using a combination of chromatin immunoprecipitation and DNA microarray hybridization (ChIP-chip analysis) did not reveal any conserved sequences among members of the B. subtilis CodY regulon (20). It has been proposed that CodY recognizes and binds a three-dimensional structure formed by AT-rich DNA (22). CodY contains a C-terminal helix-turn-helix motif that is highly conserved in different bacterial species containing a homologue of CodY and it might therefore be expected that these regulators recognize similar sequences in the respective host strains. In fact, recently it has been shown that lactococcal CodY is able to modulate the activity of a B. subtilis CodY target (18). In order to identify additional targets of L. lactis CodY and to assess whether this regulator is as pleiotropic as its B. subtilis counterpart is, DNA microarray experiments were carried out in which the transcriptional profile of L. lactis MG1363 was compared to that of its codY mutant. By

combining transcriptomics data with bioinformatics tools, a conserved motif in the regulatory regions of members of the L. lactisCodY regulon was identified. The importance of this DNA element for CodY-mediated regulation was investigated.

MATERIALS AND METHODS

Bacterial strains, media and preparation of cells for RNA isolation - Lactococcus lactis MG1363 and L. lactis MG1363 codY (Table 1), which contains a 423-base pairs (bps) internal deletion in the codY gene (16), were grown at 30 C in M17 broth (33) supplemented with 0.5% glucose (GM17). Cells were grown until the mid-exponential phase of growth (OD600~1.0). Approximately 5x109 cells (50 ml of culture) were harvested by centrifugation for 1 min at 10,000 rpm and 20 C. Cells were resuspended in 2 ml ice-cold growth medium. After the addition of 500 μl phenol/chloroform, 30 μl 10% SDS, 30 μl 3 M NaAc (pH 5.2) and 500 mg glass beads (diameter 75-150 μm), cells were frozen in liquid nitrogen and stored at -80 C until RNA isolation. DNA microarray analysis - DNA microarray experiments were essentially performed as described (34). In short, RNA was isolated from four separately grown replicate cultures of L. lactisMG1363 and L. lactis MG1363 codY, prepared as described above. Subsequently, single-strand reverse transcription (amplification) and indirect labeling of 25 μg of total RNA, with either cy3- or cy5-dye, were performed (including a sample in which the dyes were swapped to correct for dye-specific effects) using the CyScribe Post Labeling Kit (Amersham Biosciences Europe Gmbh, Roosendaal, the Netherlands). Labeled cDNA samples were hybridized to slides representing 2110 ORFs of L. lactis IL1403 spotted in duplicate and constructed as described (34,35). After overnight hybridization, slides were washed for 1 min at room temperature in [2x SSC, 0.5% SDS] and 5 min in [1x SSC, 0.25% SDS] to remove non-specifically hybridized cDNAs. Slides were scanned using a GeneTac LS IV confocal laser scanner (Genomic Solutions Ltd., MI, USA). Subsequently, individual spot intensities were determined using ArrayPro 4.5 (Media Cybernetics Inc., Silver Spring, MD). Slide data

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were processed and normalized using MicroPrep(35,36), which yielded average ratios of gene expression of mutant over wild-type (WT) strain from the data of replicates. Expression of a gene was considered to be significantly altered when its ratio of expression in the mutant compared to the WT was >1.5 and had a p-value <0.001 and false discovery rate <0.05 that were determined as described previously (35,37). When a significantly upregulated gene formed part of an operon, other members of that transcriptional unit were included, providing that they showed coregulation. A combined p-value was calculated by multiplying their individual p-values. All DNA microarray data obtained in this study are available online (http://www.ncbi.nlm.nih.gov/projects/geo/query/acc.cgi?acc=GSE2823). In addition, the slide images and raw data are available at http://molgen.biol.rug.nl/publication/cody_data/.Identification of DNA motifs - To identify conserved DNA motifs, DNA sequences encompassing 200 bps of the upstream regions of the genes that were derepressed to the highest extent in the codY mutant in the DNA microarray experiments were collected from the genome sequence of L. lactis MG1363 (L. lactis MG1363 sequence information was contributed prior to publication by Zomer, Wegmann, O’Connell-Motherway, Goesmann, van Sinderen, Shearman, Gasson, Buist, Kuipers and Kok, and is available in supplementary Fig. 1). The regions upstream of oppD, pepC, pepN, prtP and prtM were also included. This dataset was used as input for the MEME software tool (38) to search for overrepresented sequences. A graphical representation of the identified motif was obtained using Genome2D software (39). A string search for the occurrence of identified motifs was performed in the genome of L. lactis MG1363. Alternatively, Genbank files containing the entire genomes of L. lactis IL1403 (40), B. subtilis 168 (41) and S. pneumoniae R6 (42) were used as templates. Hereto, a position-specific weight matrix of the overrepresented motif was generated using Genome2D software (39), which was used to scan the genomic sequences. Results of all motif searches are available in supplementary Tables 1-5.DNA preparation, molecular cloning and transformation - Routine DNA manipulations

were performed as described (43). Total chromosomal DNA from L. lactis was extracted as detailed previously (44). Minipreparations of plasmid DNA from L. lactis were made using the High Pure Plasmid isolation Kit from Roche Molecular Biochemicals (Mannheim, Germany).Restriction enzymes, T4 DNA ligase and DNA polymerases were purchased from Roche Molecular Biochemicals. PCR amplifications were carried out using either Pwo DNA polymerase for cloning purposes or Taq DNA polymerase for colony PCR. PCR products were purified with the High Pure PCR product purification kit (RocheMolecular Biochemicals). Electrotransformation of L. lactis was performed using a Bio-Rad Gene Pulser (Bio-Rad Laboratories, Richmond, Calif.) as described earlier (45).

Combinations of oligonucleotides ctrA-Pfor with ctrA-Prev2, asnB-F with asnB-R or codY-Pfor with codY-Prev (Table 2) were used to amplify the upstream regions of ctrA, asnB and codY, respectively, from chromosomal DNA of L. lactis MG1363. The PCR products were digested with XbaI and PstI and transcriptionally fused to the promoterless E. coli lacZ gene in the integration vector pORI13 (46) digested with the same enzymes. The resulting plasmids, pORI::PasnB, pORI::PasnB and pORI::PcodY, respectively, were made in L. lactis LL108 (47), isolated and introduced into L. lactis MG1363 and L. lactis MG1363 codY by co-electroporation with pVE6007 (Table 1), a plasmid that specifies a thermo-sensitive RepA protein that can drive pORI13 replication (48). DNA fragments derived from PywcC, containing a perfect CodY-box spaced with 5-bps or 10-bps its promoter, were obtained by PCR using combinations of oligonucleotides ywcC-end with ywcC-FboxP5 and ywcC-FboxP10, respectively. These fragments were digested with XbaI and EcoRI andtranscriptionally fused to the promoterless E. colilacZ gene into the reporter plasmid pILORI4 (49). The resulting plasmids, pIL::PywcCp5 and pIL::PywcCp10, respectively, were introduced into L. lactis MG1363 and L. lactis MG1363 codY by co-electroporation. Similarly, PywcC variants containing a randomized CodY-box sequence were obtained using combinations of oligonucleotides ywcC-end with ywcC-FboxR5 and ywcC-FboxR10.

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Determination of -galactosidase activity -

Overnight cultures of L. lactis grown in GM17 were diluted to 1% in 50 ml of the same medium containing 2.5 g/ml of both erythromycin and chloramphenicol (Sigma Chemical Co., St. Louis, Mo.) for the maintenance of pORI13 and pVE6007. Cell samples were collected by centrifugation and -galactosidase activities were determined as described previously (50). In vitro DNA binding assays - EMSAs were carried out essentially as described previously (17). In short, purified PCR products were end-labeled with [ -32P]-ATP and polynucleotide kinase (Amersham Pharmacia Biotech). Combinations of oligonucleotides dppP-Pfor with dppP-Prev, asnB-F with asnB-R, ctrA-Pfor with ctrA-Prev2, opp-1 and opp-3, thrA-Pfor with thrA-Prev and argG-2 with argG-3 were used to prepare DNA probes that comprise the (putative) promoter sequences of dppP, asnB, ctrA, oppD, thrA and argG, respectively (Table 2). For labeling of the ywcC variants, the same fragments as those for cloning purposes were used. Binding reactions were carried out in 20 l volumes containing 20 mM Tris-HCl (pH 8.0), 8.7 % (v/v) glycerol, 1 mM EDTA (pH 8.0), 5 mM MgCl2, 100-250 mM KCl, 0.5 mM DTT, labeled DNA fragment (3000 cpm), 1 g BSA, 1 g of poly(dI-dC) (Amersham Pharmacia Biotech), and varying amounts histidine-tagged CodY protein (H6-CodY), purified as described previously (17). After incubation at 30 C for 15 min, protein-DNA complexes were separated in 4% polyacrylamide gels, run in TBE buffer at 100 V for 1 hr, which were dried after electrophoresis and used for autoradiography (17).

DNaseI footprinting analyses using purified H6-CodY was performed essentially as described previously (17). Reactions were performed in the absence of BCAAs. DNA fragments were prepared by PCR. Combinations of oligonucleotides serC-Pfor with serC-Prev, asnB-F with asnB-R, ctrA-Pfor with ctrA-Prev2, codY-Pfor with codY-Prev, and gltA-Pfor with gltA-Prev (Table 2) were used to prepare DNA probes that comprise the (putative) promoter sequences of serC, ctrA, codY and gltA,respectively. A DNA fragment of the codY-upstream region containing a mutated CodY-box was obtained using a two-step PCR procedure.

PCR products obtained with combinations of oligonucleotides codY-Pfor with codY-Rbox2 and codY-Prev with codY-Fbox2, were used as a template for a second PCR, using oligonucleotides codY-Pfor and codY-Prev.

RESULTS

Role of CodY in global gene expression - In order to identify the genes that constitute the regulon of L. lactis CodY, the transcriptional profile of L. lactis MG1363 was compared to that of L. lactisMG1363 codY, a strain containing a 423-bps internal deletion in codY (16). L. lactis CodY exerts strong repressing activity in rapidly growing cells in media containing excess nitrogen (15). Therefore, the cells used for the transcriptional analyses were cultured in GM17 medium and harvested in the exponential phase of growth. Under these conditions, both strains grow similarly, although the mutant has a somewhat longer lag phase (data not shown). RNA samples were prepared from each strain and, following cDNA synthesis and labeling, hybridized to DNA microarrays. Analysis of the DNA microarray data of four biological replicates revealed that the expression of approximately 30 genes was significantly influenced by the codY mutation (Table 3). Of these, the only gene of which the transcript level did decrease significantly was, as expected, codY itself (data not shown).

As anticipated, the levels of transcription of the genes that constitute the opp operon were elevated in L. lactis MG1363 codY, as this operon has previously been identified as being repressed by CodY (13,17). Although purified histidine-tagged CodY has been shown to directly interact with the upstream regions of the genes encoding the peptidases pepN and pepC, their expression levels were not significantly changed or only marginally elevated (below 1.5 fold), respectively, in the codY mutant (17).

The majority of the proteins specified by the derepressed genes fall into the functional category of amino acid transport and metabolism. The strongest derepressed transcriptional unit in L. lactis MG1363 codY from this category was the opt operon comprising optSABCDF. The coding regions of opt of L. lactis IL1403 are over 90% identical with those of dpp (dppAPBCDF) of L.lactis MG1363. As they have a similar genetic

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organization, opt is the L. lactis IL1403 counterpart of dpp, encoding a binding-protein-dependent ABC transporter for dipeptides (11,12). In fact, recently it has been shown that both transport systems have similar substrate specificities (10). As is the case for the known CodY targets, expression of dpp/opt is repressed in peptide-rich media and especially in media containing peptides with BCAA residues (11,13). These observations demonstrate that dpp/opt is another member of the CodY regulon. The transcript level of ctrA, encoding a putative cationic amino acid permease, increased more than 5 times upon deletion of codY.

A different group of genes, the transcription of which was found to be elevated in L. lactis MG1363 codY, encompasses those involved in BCAA metabolism; the ilv-ald operon for BCAA biosynthesis (51,52) was derepressed over five times. Thus, although L. lactis MG1363 like many other lactococcal dairy strains is auxotrophic for these amino acids, several genes of the BCAA biosynthetic operon are present on the chromosome and actively transcribed (1,53). The gene encoding the aminotransferase BcaT, catalyzing either the first step of aromatic or branched-chain amino acid catabolism or the last step of their biosynthesis (54,55), was also significantly derepressed.

Transcription of a number of genes involved in the metabolism of certain amino acids, other than BCAAs, was also affected by the mutation in codY. Especially, members of the histidine biosynthetic his operon, and a number of genes specifying enzymes of the arginine deiminase (ADI) pathway (56), were strongly derepressed in L. lactis MG1363 codY.Expression of the gene encoding a putative asparagine synthetase, asnB, was elevated over 4 times in the codY strain, as was the case for gltDB,the product of which is predicted to catalyze the same reaction (57).

Another gene cluster not previously known to be controlled in L. lactis by CodY contains genes involved in the Krebs oxidative cycle (58). Expression of citrate synthase (gltA), isocitrate dehydrogenase (icd) and especially aconitase (citB) was derepressed in L. lactis MG1363 codY. These results suggest that, as is the case in B. subtilis (20,29), CodY might be

involved in regulation of both nitrogen and carbon metabolism in L. lactis.

Verification of DNA microarray results of asnB and ctrA using lacZ fusions - In order to validate part of the obtained transcriptome data, DNA fragments carrying the putative promoter regions of asnB and ctrA were transcriptionally fused to lacZ in the reporter plasmid pORI13 (46) and introduced into L. lactis MG1363 and L. lactisMG1363 codY. -Galactosidase activity was monitored during growth in GM17, the same medium as was used in the DNA microarray experiments (Fig. 1A). Whereas the absolute -galactosidase activities of the two constructs were rather different (the lacZ transcription level achieved by the PasnB-containing fragment was more than 25 times lower than that of the PctrA fragment), their derepression in L. lactisMG1363 codY compared to the parent strain was similar (almost 10-fold for both). These results show that active promoter elements are present in the upstream regions of these genes and confirm the role of CodY in their transcriptional regulation.

Interaction of CodY with several of the new CodY targets - To distinguish whether repression of some of the newly identified targets by CodY occurs directly or indirectly, EMSAs were performed using purified H6-CodY (Fig. 2A). The EMSAs show that purified H6-CodY was capable of forming several protein-DNA complexes with radioactively labeled DNA fragments containing about 200 bps of the upstream regions of dppA (the first gene of the dpp operon), asnB, and ctrA,as was the case for the well-studied oppD, pepNand pepC promoters (17). These results indicate that CodY probably directly controls expression of these genes. Moreover, lactococcal H6-CodY also interacted with the putative regulatory regions of gltA and serC, as demonstrated below in DNaseI footprinting experiments. In some of the DNA binding experiments, bands of lower electrophoretic mobility than that of the free probe were observed irrespective of the presence of H6-CodY. These bands probably correspond to single stranded probe, resulting from the high AT content of the DNA fragments used (17).

An overrepresented motif is present in the upstream regions of a number of the CodY-

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repressed genes - Although interaction of CodY with several of its targets in both B. subtilis and L.lactis has been reported, a consensus CodY binding site, if any, remained elusive. In order to asses whether the members of the L. lactis CodY regulon identified here might share such a sequence motif in their regulatory regions, an in silico sequence analysis was performed. A dataset was generated containing only the upstream regions of the genes that were derepressed to the highest extent in the codY mutant (Table 2). We assumed that these genes are most likely to be under direct control of CodY and could, if it exists, contain a CodY binding site. The upstream regions of pepC and pepN, which are known to be direct targets of CodY (17), were also added to the dataset. In addition, the intergenic region of the divergently transcribed and plasmid-located prtPand prtM genes of L. lactis subsp. cremoris SK11 was included, as purified H6-CodY was shown to bind to this region in in vitro DNA binding studies (16). Since operator sites of regulatory proteins in bacteria are usually located close to their target promoters, fragments of 200 bps were chosen such that they encompassed the known or predicted promoter sequences of their cognate genes. In those cases where a complete operon was derepressed in the codY mutant, the upstream region of the first gene of the transcriptional unit was selected (i.e for ilv, his, opp anddppAPBCDF). Of the latter operon, the region preceding dppP was also included in the dataset, since putative promoter elements are present in this area. This dataset of 13 sequences was examined for the occurrence of common elements using the MEME algorithm (38). As there was no prior knowledge about a possible CodY binding site, MEME was not restricted with respect to the motif width and the number of repetitions and was allowed to search on either of the two DNA strands. MEME was set to search only for inversely repeated (IR) sequences, as most DNA binding proteins are known to bind sequences with such an organization. These parameters prevented common upstream elements (-35 and -10 sequences and the ribosome binding site) from concealing the presence of possible CodY binding sites. Application of the pattern recognition program revealed the presence of an overrepresented motif in a number of the DNA sequences of the dataset (Fig. 3) with homology to

the upstream half-site of a palindromic sequence found to be important in oppD regulation (17). Derivates of this 15-bps IR cis-element, AATTTTCWGAAAATT, are present in the upstream regions of 11 of the 13 genes that constitute the input data for the program (Table 4). A well-conserved copy of this motif (designated CodY-box) seems to be absent from the upstream regions of hisC and pepN. Interestingly, the upstream regions of the operons that show the highest fold-difference in expression in L. lactisMG1363 codY compared to L. lactis MG1363 contain multiple copies of the CodY-box. Two copies of the motif are present close to dppA, oppAand ilvD, whereas three copies can be discerned in the regions preceding ctrA and gltA.

To address whether copies of the CodY-box are present in the proximity of any of the other genes affected by the codY mutation (the ones that were not used to generate the dataset for MEME)and in genes which were not affected in our transcriptome analysis, the entire genome of L. lactis MG1363 was searched for the occurrence of this motif using Genome2D software (39). Using a weight matrix (Fig. 3), derivates of the CodY-box were found throughout the lactococcal genome and were mainly located in intergenic regions. These were ranked according to their similarity with the consensus (supplementary Table 1). Obviously, high-scoring motifs were found in the non-coding sequences that were used to build the weight matrix, but derivates of the motif were also found upstream of several other genes.

Purified CodY binds to sequences containing a CodY-box in vitro - To examine whether there is a relation between the occurrence of the CodY-box and the ability of CodY to bind DNA in vitro,DNaseI footprinting experiments were performed using radioactively labeled fragments of about 250 bps encompassing the (putative) promoter regions of gltA, serC or ctrA (Fig. 4). These fragments all contain well-conserved copies of the CodY-box. Addition of purified H6-CodY protein resulted in protection against nuclease activity in one or multiple regions of all the probes, which indicates that gltA, serC and ctrA, are most likely, direct targets of CodY. For all promoters, protected regions were observed that coincide with the nucleotide stretch formed by the CodY-box (Fig. 5).

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To get an indication whether CodY might have a higher affinity for DNA that contains a CodY-box, EMSAs were performed using H6-CodY and DNA probes obtained by PCR amplification of a number of the regions encompassing the best-scoring derivates of the CodY-box in L. lactis MG1363. Indeed, binding patterns similar to the ones presented in Fig. 2Awere observed for all probes tested (Fig. 2B),except for the upstream region of yeaG for which H6-CodY was able to shift only a small fraction of the probes. H6-CodY was not able to bind to a negative control, an AT-rich DNA fragment containing the upstream region of the B. subtilis comG gene. Some H6-CodY binding occurred to the upstream region of L. lactis argG, whose transcription was found unaffected in the DNA microarray analysis and is not preceded by a CodY-box. However, H6-CodY poorly bound to this fragment and, compared to the other lactococcal probes tested, the fraction of shifted DNA was lowest. These results clearly demonstrate that the presence of a CodY-box can be used to predict whether a CodY-DNA interaction can occur in vitro.

A CodY-box serves as an operator site for CodY - Whether the presence of a CodY-box is sufficient to evoke CodY regulation was examined by introducing a copy of the motif in front of a gene that is not regulated by CodY. The gene ywcC was selected as a candidate from the DNA microarray data, since it was actively transcribed under the growth conditions applied and its expression was unaffected by the codY mutation. Four different variants of the upstream region of ywcC were obtained by PCR. They contained either a perfect or a randomized copy of the CodY-box, and were introduced either at 5- or 10-bps upstream of the putative promoter of ywcC, placing the motifs at opposite sides of the helix. First, the ability of CodY to bind to these ywcC promoter variants was tested in EMSAs (Fig. 6A). Purified H6-CodY was able to form a stable protein-DNA complex with both variants containing the artificial CodY-box in vitro, but not with the fragments containing a randomized box.

To find out whether the difference in binding is reflected in in vivo regulation by CodY, the different ywcC promoter variants were fused to promoterless lacZ in pILORI4 and introduced into

L. lactis MG1363 and L. lactis MG1363 codY.Expression of lacZ expression was monitored during the exponential phase of growth in nitrogen-rich medium (Fig. 6B). No derepression was observed in the codY strain containing the randomized box or the variant carrying the consensus CodY-box located 5-bps upstream of the -35 sequence. Expression of the reporter construct containing a perfect CodY-box located at 10-bps upstream of the -35 consensus was almost 10-fold increased in the codY mutant relative to that in the wild type strain. This ratio is comparable to the ratios obtained for asnB and ctrA, two of the most prominent targets of codYfound in the DNA microarray experiments (Table 3, Fig. 1). Thus, a CodY-box can serve as an independent functional motif responsive to CodY protein in vivo.

The codY promoter region contains a CodY-box and is auto-regulated - As a highly conserved copy of the CodY-box was found 86-bps upstream of codY itself and a CodY-box serves as an operator site for CodY, it could very well be that CodY regulates its own transcription. To examine this, a DNA fragment carrying the CodY-box and putative codY promoter sequences were transcriptionally fused to lacZ in the reporter plasmid pORI13 and introduced into L. lactisMG1363 and L. lactis MG1363 codY. -Galactosidase activity was monitored during growth in nitrogen-rich medium (GM17), where high CodY-activity is ensured (15,17). In both strains, the expression driven by PcodY was highest in the exponential phase and dropped to a lower (constant) level in the stationary phase of growth (Fig. 1B). Deletion of codY resulted in a 3- to 4-fold increase of -galactosidase expression, indicating that CodY represses its own synthesis under these conditions. DNaseI footprinting experiments revealed that CodY could interact with the upstream region of its own gene in a BCAA-dependent manner (Fig. 7), as the presence of at least one of the cofactors of CodY, Ile, was required. The region upstream of CodY that is protected by H6-CodY contains a CodY-box. H6-CodY did not protect a fragment in which the CodY-box was replaced by an unrelated sequence (CTAAGCGGCCGCTGA), irrespective of the presence of BCAAs, showing that the presence of a CodY-box is required for CodY-binding (Fig. 7).

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Presence of the CodY-box in other bacterial species - In order to assess whether sequences homologous to the CodY-box are also present in other bacteria containing a CodY protein, a search was performed in the genomes of the Gram-positive bacteria L. lactis subsp. lactis IL1403, B.subtilis 168 and S. pneumoniae R6. If the CodY-box would also serve as an operator site for CodY in these organisms, such a comparison could reveal subtle differences in the consensus sequence between the various organisms. As shown in supplementary Tables 2-4, derivatives of the motif were identified in the genomes of L. lactis IL1403, S. pneumoniae R6 and in the upstream sequences of a number of the known CodY-regulated genes of B. subtilis (e.g. hutP anddppA). Interestingly, repression of the latter gene in a B. subtilis codY deletion strain could be complemented by L. lactis codY, indicating that lactococcal CodY can recognize similar sequences in B. subtilis (18). Recently, a genome-wide gene expression analysis of the B. subtilis codY mutant was reported (20). Using the upstream nucleotide sequences of the targets found in that study, we searched for the occurrence of the putative CodY-box in these sequences. Although the similarity scores with the consensus where not very high, derivates of the CodY-box were identified in some of these sequences, indicating that a similar motif might be operational in B. subtilis (supplementary Table 5). As the L. lactis strains IL1403 and MG1363 are over 85% identical at the nucleotide level, CodY-box sequences were identified at similar positions in the L. lactis IL1403 genome. In the genome of S. pneumoniae R6, highly conserved copies of the CodY-box were found upstream of genes (putatively) involved in nitrogen metabolism and especially of those concerned with the biosynthesis of BCAAs. Interestingly, the CodY-box is present upstream of ppmA and rgg, two genes that are known to be involved in virulence of this human pathogen (59,60). In contrast to B. subtilis, a CodY-box is present in the upstream region of S. pneumoniae R6 codY, which suggests that transcription of codY of the latter organism, like that of L. lactis, is auto-regulated.

DISCUSSION

In the last number of years, the knowledge about the pleiotropic regulator CodY has expanded rapidly. A large number of genes in B. subtilishave recently been shown to be regulated by this transcriptional repressor (20) . The current study defines the regulon of L. lactis CodY and shows that deletion of the regulator has global effects on gene expression. In addition to the known members of the lactococcal CodY regulon, which are all involved in the degradation of casein and in peptide- and amino acid uptake and metabolism, the newly identified genes also predominantly belong to this category. Apparently, when the cells reach the stationary phase and nutrients become scarce, CodY-mediated repression of peptide- and amino acid transport systems is relieved in order to maintain the intracellular nitrogen balance. As the major peptide uptake systems are fully derepressed in L. lactis MG1363 codY, intracellular nitrogen pools are probably severely altered. The expression of genes (putatively) involved in the metabolism of a number of amino acids other than BCAAs, especially of genes connected to asparagine, glutamate and histidine biosynthesis and of those required for arginine catabolism, was found to be strongly affected as well, which might be a way to counteract the effects of removal of codY on intracellular nitrogen availability.

Because of its broad effects on the proteolytic system and amino acid metabolism, it is rather surprising that the activity of lactococcal CodY seems to be modulated solely by BCAAs (15,17,18) and not by a more general signal of nitrogen availability. By using BCAAs as direct signaling molecules for CodY, L. lactis could ensure a proper supply of BCAAs, for which most dairy strains are auxotrophic (1). Moreover, BCAAs serve an important role in the synthesis of fatty acids and determine protein hydrophobicity. The central role of BCAAs in CodY-mediated regulation is reflected by the fact that the ilvoperon is one of the strongest derepressed transcriptional units in L. lactis MG1363 codY, as was also the case in B. subtilis (19,20,27,28). Although the lactococcal strain used in this study cannot synthesize all enzymes required for BCAA biosynthesis, due to nonsense mutations and small deletions in ilv, the encoding genes (including the downstream aldB gene) are still present, actively transcribed and tightly regulated (1). As we show that this operon is one of major targets of CodY

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(Table 3) and CodY-boxes are present in its upstream and coding regions (Table 4), CodY most probably directly controls ilv expression. Moreover, repression of this operon has been shown to be dependent on the BCAA Ile (51-53), which is the most potent modulator of CodY activity, as it has been shown that CodY binding to the promoter region of at least one of its targets, oppD, in DNA binding studies is stimulated most by this particular BCAA (17).

The effects of the deletion of codY in L.lactis were not restricted to genes involved in amino acid uptake and metabolism alone. In particular, expression of the gltA-citB-icdtranscriptional unit, which encodes part of the Krebs oxidative (TCA) cycle, was altered. As these genes are actively transcribed in the strain used in this study, and a number of them are known to encode functional proteins (those constituting the oxidative branch) in related lactococci (61), our results suggest that L. lactisMG1363 CodY, like its B. subtilis counterpart, might be involved in regulation of both nitrogen and carbon metabolism (20,29). The oxidative branch of the TCA cycle can provide the cell with

-ketoglutarate ( -KG), which, in turn, ise used in the formation of glutamate by some LAB (58,62). In addition, -KG acts as a co-substrate for the aminotransferase BcaT, which catalyzes the first step of BCAA catabolism (55). Thus, -KGprovides a connection between BCAA and glutamate metabolism, which could explain why CodY orchestrates transcription of genes involved in the TCA cycle and glutamate biosynthesis (gltDB and lysA) in addition to those concerned with BCAA metabolism (ilv and bcaT). Although these genes are, apparently, linked at the transcriptional level, their biological role remains uncertain as some of the enzyme activities required for these reactions have not been determined in the lactococcal strain used in this study.

Expression of the gene encoding the aminotransferase BcaT has recently been shown to be controlled by CodY (54). The bcaT gene is repressed by CodY in a chemically defined medium supplemented with casitone, a complex source of nitrogen and, in that respect, comparable to the GM17 used in this work (13,33). Although expression of bcaT was significantly altered (p<0.001) in our experiments as well, the extent of

derepression measured on the DNA microarrays was somewhat low compared to that observed by Chambellon and Yvon (54). Changes in mRNA levels were lower for all the genes examined here for which CodY repression ratios have already been determined, yet the trends are comparable (13,15-17). Compression of the observed differential expression becomes apparent from comparing Fig. 1 with the relevant data in Table 3. This effect has been shown to be inherent to the DNA microarray methodology (63) and might explain why not all previously identified CodY targets were found in this study. Alternatively, it could be that these genes are regulated by other (unknown) mechanisms that repress transcription under the conditions applied here.

To get an indication whether the genes affected in the codY mutant were under direct or indirect control of CodY, the upstream regions of a number of them were tested for their ability to complex with purified H6-CodY (Fig. 2). Inspection of the DNA sequences did not initially reveal common motifs. A more comprehensive bioinformatics approach using the upstream regions of only those genes that were derepressed to the highest extent, led to the identification of an inversely repeated motif, AATTTTCWGAAAATT, that was present in most of the sequences constituting the dataset. This motif (designated as CodY-box) shows homology to the upstream half-site of a palindromic sequence known to be important in oppD regulation (17). That study reported, among others, the analysis of several mutants that showed distorted CodY binding and regulation. Of these mutants, the ones that were most affected in oppregulation contained deletions and base pair substitutions within the stretch of nucleotides containing the CodY-box identified here. Here we show that this motif functions as an operator site for CodY. Multiple copies of the CodY-box are present in the intergenic regions of some transcriptional units, which might serve regulatory purposes: they could increase the affinity of CodY resulting in stronger repression. Similarly, orientation and similarity of the motif with its consensus sequence, of which the nucleotides at positions 3, 6, 7, 9, 10 and 13 are most strongly conserved (Fig. 3), might also contribute to strength of regulation of a target gene by CodY. We show that the position of the DNA motif is

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important for effective regulation, as a 5-bps difference in variation of the distance of the box relative to the promoter determines whether the downstream gene is CodY-regulated (Fig. 6). As a difference of 5-bps equals half a helical turn, it places the CodY-binding site on the opposite side of the DNA helix. These experiments show that repression by CodY might be helix-face dependent. However, we cannot exclude the possibility that loss of CodY-mediated repression is caused by less efficient binding of CodY protein to its target DNA sequence. Most DNA binding proteins preferentially bind, either, to the major or minor groove in DNA. Introduction of half a helical turn of DNA would place the CodY-binding site in the opposite groove, which could negatively affect the efficiency of binding. X-ray crystallographic studies or DNA binding studies using interfering drugs would be helpful to get a better understanding of the molecular mechanisms of CodY-binding.

A well-conserved copy of the CodY-box was found about 80 bps upstream of the L. lactiscodY start codon. Using in vitro DNA binding assays and a PcodY-lacZ fusion, we show that CodY binds to the upstream region of its gene invitro and represses its own synthesis in vivo (Fig. 1 and 7). Like in B. subtilis (21), expression of L. lactis codY is highest in the exponential phase of growth and decreases when cells enter the stationary phase. Although B. subtilis codYexpression seems to be derepressed in minimal media lacking amino acid sources (20), it remains to be elucidated whether B. subtilis codY is also subjected to auto-regulation, especially since no obvious derivate of the CodY-box could be identified in its upstream region (supplementary Table 4). Auto-regulation provides an additional level of regulation of the CodY regulon, next to that exerted by BCAAs through modulation of the activity of CodY. In B. subtilis, GTP, as an alternative for auto-regulation, could provide this additional level of regulation. The lactococcal PcodY-lacZ fusion construct was used to show that transcription of codY in the WT strain is low in media containing an excess of amino acids and peptides (in the form of casitone). Transcription driven from PcodY is derepressed when the concentration of casitone is lowered (data not shown), which fits well with the results presented in Fig. 7, where the presence of the BCAA Ile was

required for binding of lactococcal H6-CodY to the codY promoter fragment. A decrease in the basal activity of the codY promoter when cells approach the end of exponential growth, together with a concomitant relief of BCAA acid-mediated repression by CodY protein of its own transcription, might ensure that a certain amount of CodY remains present, allowing the cell to rapidly respond to changes in BCAA availability.

It has recently been shown that lactococcal CodY is able to modulate expression of B. subtilisdpp, encoding the dipeptide permease operon, in a B. subtilis codY mutant (18). Thus, both B. subtilisand L. lactis CodY must be able to recognize similar sequences, which was anticipated as their DNA binding domains are highly conserved (15). Other studies in B. subtilis have identified regions important for medium-dependent regulation of and/or for CodY binding to the promoter region of this gene (21,22). Interaction of purified B. subtilisCodY with the upstream region of dpp was affected by several mutations in a short region close to its transcription start site. At the time it was unknown that this region contains a sequence (AATATTCATAATTTA) that resembles the CodY-box identified in our current study and forms part of a high-affinity site for B. subtilisCodY (64). These binding studies showed that, with increasing concentrations of CodY, the protein was able to bind to several low-affinity sites as well. Our footprinting data suggest that lactococcal CodY binding to the upstream regions of gltA, serC and codY might occur in a similar manner. In addition to the region containing the CodY-box, multiple areas that are protected against DNaseI activity can be distinguished, which might indicate that CodY can also bind to multiple sites in these promoters. As deletion of the CodY-box in PcodY resulted in total loss of protection (Fig. 7), CodY might need a high-affinity binding site, formed by the CodY-box, to be able to bind to other, low-affinity, sites when intracellular levels of CodY protein or BCAAs are low.

Both deletion and mutational analyses of the operator region of the B. subtilis histidine utilization operon (hut) showed that an AT-rich stretch in the area from +10 to +24 relative to the transcription start site is required for amino acid-mediated regulation exerted by CodY (65,66). As for the B. subtilis dpp operon (see above), these

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results can now be explained since the identified region overlaps with the CodY-box (AGTTATCAGAATTTT) found in this study. As we show here that CodY-boxes are present in several Gram-positive bacteria, it is tempting to speculate that this motif serves as a general CodY binding and regulatory site.

The CodY-box could not be discerned in the upstream regions of all the differentially expressed genes (e.g. of pepN and hisC) by the bioinformatics tools used in this study. However, close inspection of the pepN upstream region did reveal a putative CodY-box (AATTTTCTATTCAAT). As this box is much less conserved than the ones present upstream of transcriptional units that were strongly derepressed upon functional removal of codY (Table 3), it might explain why expression of this well-known CodY-target was not found to be significantly changed in our DNA microarray experiments. Absence of a CodY-box upstream of a gene affected by the codY mutation could indicate that its change in expression is an indirect effect of the mutation. Alternatively, it could be that other sequences play a role in the recognition and regulation of these genes by CodY. Transcriptional regulation of the CodY-dependent genes required for production of the proteinase PrtP of L. lactis SK11 has been investigated previously (16,67). A mutational analysis of the intergenic region between prtP and prtM

pinpointed an IR other than the CodY-box as being required for nitrogen-dependent regulation of the activity of the promoter. Previous studies in B. subtilis have not pin-pointed a consensus sequence for CodY binding and it has been proposed that CodY might recognize and bind a topological structure formed by AT-rich DNA (22). Such structures might be enhanced by the presence of an IR. This would also explain why regions of dyad symmetry with no apparent sequence homology were found to coincide with CodY binding to the B. subtilis ilvB (19) and citBpromoters (29). Perhaps, the presence of a specific DNA structural motif could bypass the need of a CodY-box for CodY to bind to its targets. The presence of such a DNA topology, together with a high-affinity binding site formed by the CodY-box might then result in maximum repression by CodY.

ACKNOWLEDGEMENTS

We are grateful to Aldert Zomer for his skillful assistance in the in silico analyses, Maarten Groeneveld for technical assistance in determining the expression patterns of ctrA and asnB and Jan Sikkema, Ellen Looijesteijn and Ingeborg Boels for helpful discussions. This work was supported by Friesland Foods Corporate Research and the Dutch ministry of Economic Affairs (SENTER).

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FIG. 1. Expression pattern of CodY-regulated genes. L. lactis MG1363 and L. lactis MG1363 codY,carrying fusions of the upstream region of asnB, ctrA (panel A) or codY (panel B), respectively, to lacZ in pORI13, were grown at 30 C in GM17. -Galactosidase activity was measured in time samples. Growth curves of L. lactis MG1363 (open diamonds) and L. lactis MG1363 codY (open squares) are shown as well as -galactosidase activity in L. lactis MG1363 (diamonds) and L. lactis MG1363 codY (squares).The experiment was carried out in triplicate. Error bars indicate standard deviations.

FIG. 2. Electrophoretic mobility shift assays using purified H6-CodY. Probes were obtained by PCR and contain the upstream regions of CodY-regulated genes identified in DNA microarray analysis (panel A)and genes that contain a derivate of the CodY-box (panel B). Radioactively labeled probes containing approximately 200 base pairs of the upstream regions of dppP, asnB, ctrA, oppD, thrA, ygjD, feoA, or yeaG were incubated alone or with increasing amounts of H6-CodY (as indicated in nM above each lane). The positions of free probe and CodY-probe complexes are indicated in the left margin by arrows and brackets, respectively. Fragments containing the upstream region of L. lactis argG and B. subtilis comGserved as negative controls.

FIG. 3. Overrepresented motif contained in upstream regions of CodY-regulated genes. The conserved motif was identified using the MEME algorithm as described in Materials and Methods. The weight matrix shows the percentage of A, C, T or G nucleotides (as indicated in the legend) at each position of the motif. The inversely repeated consensus sequence (indicated by arrows) deduced from these frequencies is shown below the diagram where W can be an A or T nucleotide.

FIG. 4. DNaseI footprinting analysis of H6-CodY binding to DNA. Radioactively labeled probes containing approximately 200 base pairs of the upstream regions of gltA, serC and ctrA, all containing a CodY-box, were examined alone or with different amounts of H6-CodY (as indicated above each lane) in DNaseI footprinting analyses as described in Materials and Methods. No BCAAs were added to the binding reactions. The left and right halves of each panel represent the footprint of the upper and lower DNA strand, respectively. Footprints are flanked on the left by Maxam and Gilbert A+G sequence ladders (AG). Protected regions are marked with bars in the right margin.

FIG. 5. Summary of DNaseI footprinting analysis of results presented in Fig. 4. Protected bases are underlined. The position of the CodY-box is indicated in bold. The (putative) –35 and –10 sequences are overlined. Numbers in the right margins of the upper strands indicate distances to the respective start codons of the genes indicated in the left margin. The oppD footprinting data was obtained previously (17).

FIG. 6. H6-CodY binding and expression analysis of PywcC variants. Radioactively labeled probes of PywcC variants were examined alone or with different amounts of H6-CodY (as indicated above each lane in nM) in EMSAs (panel A). Probes contain a perfect or a randomized copy of the CodY-box at 5- (P5 and R5, respectively) or 10-bps (P10 and R10, respectively) upstream of the promoter of PywcC. The positions of free probe and CodY-probe complexes are indicated in the left margin by arrows and brackets, respectively. L. lactis MG1363 and L. lactis MG1363 codY, carrying PywcC variants P5, R5, P10 and R10, respectively, fused to lacZ in pILORI4, were grown at 30 C in GM17 (panel B). Bars indicate the ratio of -galactosidase activity in the codY mutant over wild-type MG1363 in cell samples harvested from the exponential phase of growth. The experiment was carried out in triplicate. Error bars indicate standard deviations.

FIG. 7. DNaseI footprinting analysis of H6-CodY binding to the codY promoter region. A radioactively labeled probe containing the upstream region of codY, was examined alone (lanes 1) or in the presence of 120 nM (lanes 2 and 4) or 240 nM (lanes 3) of H6-CodY in DNaseI footprinting analyses as described in

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Materials and Methods. The reactions shown in lanes 4 were performed in the presence of 7.5 mM Ile. The left and right halves of the panel show footprinting reactions using probes containing a wild type and a mutated CodY-box (regions enclosed by boxes), respectively. Footprints are flanked on the left by Maxam and Gilbert A+G sequence ladders (AG). Protected regions are marked with bars in the leftmargin.

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TABLE 1. Bacterial strains and plasmids used in this study

Strain or plasmid Relevant phenotype or genotype Source or reference

Strains

L. lactis MG1363 Lac-; Prt- ; Plasmid–free derivative of NCDO712 (68) MG1363 codY MG1363 derivative containing chromosomal deletion in codY (16) LL108 Cmr, MG1363 derivative containing multiple copies of the pWV01

repA gene in the chromosome (47)

Plasmids

pORI13 Emr; integration vector, promoterless lacZ, Ori+, RepA- derivative

of pWV01 (46)

pILORI4 Eryr; pIL252 carrying the multiple cloning site and promoterless lacZ of pORI13

(49)

pVE6007 Cmr; Temps replication derivate of pWV01 (48) pORI::PasnB Emr; pORI13 carrying a 226-bps asnB promoter fragment

amplified with primers asnB-F and asnB-R This work

pORI::PcodY Emr; pORI13 carrying a 498-bps codY promoter fragment This work pORI::PctrA Emr; pORI13 carrying a 233-bps ctrA promoter fragment amplified

with primers ctrA-Pfor and ctrA-Prev2 This work

pIL::PywcCp5 Emr; pILORI4 carrying a 146-bps ywcC promoter variant P5 This work pIL::PywcCp10 Emr; pILORI4 carrying a 146-bps ywcC promoter variant P10 This work pIL::PywcCr5 Emr; pILORI4 carrying a 146-bps ywcC promoter variant R5 This work pIL::PywcCr10 Emr; pILORI4 carrying a 146-bps ywcC promoter variant R10 This work

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TABLE 2. Oligonucleotides used in this study

Name Sequence (5’-3’)a

asnB-F AACTGCAGGATTTAGCTGACTTTGGCTACasnB-R GCTCTAGACTTCTATCGTTAAGTCAGATG ctrA-Pfor AACTGCAGGAAAGCACCAGAAGTACTGA ctrA-Prev2 GCTCTAGACGATAAAGCTCAAAATCGGC dppP-Pfor GTCTAGCTTACGACTTAAAATC dppP-Prev CCCTCTTTCATGAATTGTGTC gltA-Pfor AACTGCAGGTTGTCAAAGGTGAAGCCATTC gltA-Prev GCTCTAGAGTAAAATTCACTAGGAATTTG opp-1 GCTCTAGACACTCACTTGTTTTGCTTCC opp-3 AACTGCAGTAAAACAATAATAAAAGCAG argG-2 GCTCTAGAATCCACCTGAATATGCC argG-3 CGGAATTCACTCTGCCATGGCTCCGC serC-Pfor AACTGCAGCGCCAAAGAAGTTGAATGGAAC serC-Prev GCTCTAGAGGAAGTACACTAGGTCCTGCAC thrA-Pfor GTCAGCATTTTCATGCTATCTTC thrA-Prev GAGTAGCTGATGCGAGTGATG codY-Pfor AACTGCAGGATCATTTTCGGATTGTC codY-Prev GCTCTAGACAAATCGGTCACTCCATC codY-Fbox2 GAGTCTAAGCGGCCGCTGATTTATTGTTTTTCATG codY-Rbox2 TAAATCAGCGGCCGCTTAGACTCTCAACAAAAAAAG ywcC-end GATCTCTAGATTAAGATACACGTTTAGTATAACCGCC ywcC-FboxP5 TCGAATTCAATTTTCTGAAAATTTATTTTTGCTGAAAACGC ywcC-Fbox10 TCGAATTCAATTTTCTGAAAATTATTAATATTTTTGCTGAAAAC ywcC-FboxR5 TCGAATTCGTAATAATATTACATTATTTTTGCTGAAAACGC ywcC-FboxR10 TCGAATTCGTAATAATATTACATATTAATATTTTTGCTGAAAAC

a) Restriction enzyme sites are underlined

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TABLE 3. Summary of transcriptome comparisons of L. lactis MG1363 codY and L .lactis MG1363

Transcriptional unit

Expression

Ratiob

Significance

(p-value)c Description

d)

dppA, P, B, C, D, F 10.5 10-13 dipeptide transport system gltD, (B), lysA 6.1 10-10 glutamate biosynthesis ilvD, B, N, C, A, aldB 5.4 10-19 BCAA biosynthetic operon (hisC), Z, G, D, B, ymdC, hisH, A, F, I, K 5.3 10-22

histidine biosynthetic operon

ctrA 5.1 10-5 cationic amino acid transporter

oppD, F, B, C, A, pepO1 4.9 10-29

oligopeptide permease asnB 4.4 10-4 asparagine synthetase gltA, citB, icD 2.8 10-8 krebs TCA cycle enzymes serC, A, B 2.4 10-4 serine phosphatase arcD1, C1, C2, 2.1 10-8 arginine catabolic pathway amtB 2.0 10-4 NrgA-like protein ynaD, A, C 1.7 10-7 ABC transporter

yndA 1.6 10-5 conserved hypothetical protein

bcaT 1.6 10-4 BCAA aminotransferase ydcG 1.6 10-5 transcription regulator ynhA 1.6 10-3 hypothetical protein ydgC 1.5 10-4 amino acid permease yqaB, dapB 1.5 10-7 hypothetical proteins pi120 1.5 10-4 putative dUTPase ftsW1 1.5 10-4 cell division protein FtsW

a) Shown is the ratio of gene expression defined in b) of the gene (in an operon) that shows the highest ratio (underlined). Genes shown within parenthesis were not represented on the glass slides used in the experiment, or contained an amplicon sequence that did not share homology to L. lactis MG1363 sequences.b) Ratio: expression in L. lactis MG1363 codY over that in L. lactis MG1363. c) For operons, a combined p-value was calculated as described in Materials and Methods.d) (Possible) gene function (40).

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TABLE 4. Conserved sequences in upstream regions of members of the L. lactis MG1363 CodY regulon

Gene Locationa Strandb Sequence ctrA -30 + AATTGTCTGACAATTdppA -62 - ATTTTTCTGACAATTgltA -31 - TATTTTCTGAAAATTdppP +21 - TATTGTCAGAAAATTserC -32 + AATTATCAGAAAATToppD -77 + AATGTTCAGAAAATTdppA +11 - AATATTCTGAAAATTilvD -39 + AATGTTCTGACAAATasnB -48 + AATTTCCAGACAATTdppP -62 - TGTTTTCTGAAAATTgltB -55 - TATATTCTGATAATTgltA -5 + AATTTTCGGAATAAActrA -98 - ATTCGTCAGTAAATTpepC -32 - AATTATCAAAAAAATctrA -75 - TTTTTTCAAAAAAATprtP -74 + AATTTACAGATAAAAgltA -56 + TATTTTCTAAAAAAAilvD -86 - ATTCATCGGAATAATConsensus AATTTTCWGAAAATT

a) The location of the presented sequence is given relative to the (putative) transcriptional start site, which was determined experimentally or deduced by searching for sequences resembling consensus promoter elements. b) Orientation of the conserved sequence relative to the (putative) transcriptional start site.

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Den Hengst et al. - Supplementary material

Supplementary Fig. 1

L. lactis sequences used for the identification of overrepresented motifs among CodY-regulated genes

>dppP AGATAAAAATTTTTTTCAAAAGTTTGTGAAAAGTTTCCGCTATTAAAAAATTAAATGTTAATTTTCAGAAAACATAACCATTATACTCTACAATTCAGGTTGAATTAAGTATAATACCAATATAATAAATTTTCTGACAATAATAAAAATTGCGAAGTCAGACACAATTCATGAAAGAGGGAAATTACATGAAGACTTGG >dppA CATCATGAAACTTTCAGAAGTTGTTGAAAAATTATAATGACAAAAAAGTACTCGACAAGAGTCGGTACTTTTTAGTTTTGTTAAATTGTCAGAAAAATACAATAATATTCTTGACATTAGATTTTCGAAGAAGTATAATAGGTCCACGTTTAATTTTCAGAATATTAGAAAATTCGATAGTACTTTTAGGATTTGGAGAA >ctrAGAAAGCACCAGAAGTACTGACAGAAATTGATTTTAATAAAATAATTTACTGACGAATCTGTCAGTATTTTTTTGAAAAAAATTTTATACTGCATAAAGTTAATTCTTGACAATTGTCTGACAATTCGGTAAAATACAGTTTATTGAAATTATTTAGTTACAAATTCAGAAAAATGAGGATTTATTATGGGATTTATGAGA >oppD AAAAGCAGTTTTTAGTATGATTACTGCTTTTATTATTTCCTCCAAAACTTTTGCTTTACCTTTATTTCGCGTAATGTTCAGAAAATTCATGAACATACCTAAAATAGTAAATTTTTGCAAATATGCAGAAAAAGTAGTATACTTTTATTAAGTCTATTTAGAAAGATTTTATTGAGGTAAATATGGAAAGTGAAAATATT >pepN GAAGCAACTAAATAATTAATGACAAAAAATTGAGGATATTGATAAGAGTGAATATCCTCTGTAAAAGCTGTCAGTAGACAGTTTTTTTAATAAGTTAAAGAAAAGATGTAATTTTTCTTTGTACTCGAAATTTTCTATTCAATTTGATATAATTATATTAATACTGAATATTTAGGAGAAGATATGGCTGTAAAACGTTT >pepC TCAATGATGGCTTGAAAGTTGCGCACCCGTGGCTTTTAGAAGCAAAGAAAGATTTAGAAAATCAGCTTTCCTAGCTGATTTTTTTGATAATTTAGATTATAATAGAAGAATGTAAAAAATAATAGAATATCATTAATCAAAATCGATAATGATTATTTTTATCGAAACTTTTGTCAGAAGTTTCGATTTATTGGGAGGTA >serCCCAAAGAAGTTGAATGGAACATGTTATTACTTGATTTGTTAAATTGGTAAGATGCTGTTTAGACAGAAGTTCACATCATTGATGTGATTTTTGTCGAACAGTATTTTTTTATATTTGAATTATCAGAAAATTATATTATAATAGTGTTTAATAAATAATTTGAGGAAGTGAAATCGATGATTTATAATTTTGGTGCAGGA >ilvDTTAAGCATAAGTATTTCATTATTCCGATGAATTTTTAAAAAGAAAGCAAAAGTATTTTATAGACTTTATTGAATGTTCTGACAAATTATTGTATTTTCAATTTTTTAATGATAAAATAACTCTATAAAAATTTACGGGGAGGTCAAAAAGATAACATATGGAATTCAAATATAACGGAAAAGTTGAATCAATAGAGCTCA >hisCCTGATGCTAAGATGAACCACACTCATCGCTATCTTACTCACCAAATAATTGTGAGCGTTGGCTACGGTACTGCTGAGTTTAACATAAACTCACTGAGTCTACTTTTGTGAAAAAGTAGTAAATTAAGGTGGAACCACGACATTACCGTCCTTTAAGCCAAGTGCTTAAAGGCGCTTTTTTTGTATTATATTTATCATTTT >prtPM GCTAAATAATAACGCTAAAAGTTAATTTACAGATAAAAAAATTAATAGAAGATTAAAATTTTCGTTGAATTTGTTCTTCAATAGTATATAATATAATAGTATATAATATTATATTATATAATATA

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ATCTTAACTACATCAAGCGTAGGCTTTGATTTGGTTATGAAACTTTTGGAAAGTGGAGGATATTGGATGCAAAGG >gltBDATTCATTCTTTTATCTTATGATTTTAGATGTTTTTTGTCTATTGTAAGGGTCTTCATCTATTAGATAAAGCTATTAAAAATTACATTTATATATAATTATCAGAATATATTGATATTTCATCGAAATTTTAGTAGAATGAAAGAACCAAATTGTAAAATAAAAGAGGTTGTGTTATGAATAAAGAAGCTAAACAAGCCAT >gltA/citB/icd GAAGCCATTCAAACACAAGACTTATTGATTGAAATTGACTAACTTTAAATTAACCCTACCATTATGGTAGGATTTTTTATTTTCTAAAAAAAAGTAATTTTAATTTTCAGAAAATATATAATTTTCGGAATAAAAAGTGTATAATAATGAAATAGATGGAGGTATTTATGAATTTAATGAATAAAGAAGAAAAAATGATT >asnB TTAAAATTAAAAATGATTGGCGCGACCGTAAAATGGATTTAGCTGACTTTGGCTACAATCGTGATGATTATATGTAATGAAAATAGCGAATTATCGCTATTTTTTGTTTTATTATGAAATTTCCAGACAATTGTGATATAATATTGAAAATTATAATTATTATTGGGGGAAATTATGTGCGGTTTTTTATTTATGGAAAC

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Supplementary TABLE 1. Occurrence of CodY-box derivates in the genome of L. lactis MG1363

Gene Positiona Sequence Scoreb

dppP 278 AATTTTCAGAAAATT 11.8 codY 86 AATTGTCAGAAAATT 11.3 serC 44 AATTTTCTGATAATT 11.3 thrA 56 AATTTTCAGATAATT 11.3 ygjD 103 ATTTTTCAGAAAATT 11.3 ytjF 195 AATTTTCGGAAAAAT 11.3 gltA 51 AATTTTCAGAAAATA 11.2 feoA 68 ACTTTTCAGAAAATT 11.1 yghD 44 AATTTTCTGAATATT 11.1 nrdF 187 ATTTTTCAGAAAAAT 11.1 ctrA 60 AATTGTCAGACAATT 10.9 dppA 108 ATTTTTCTGACAATT 10.9 oppD 95 AATTTTCTGAACATT 10.9 metA 195 ATTTTTCCGAAAATT 10.9 ychG 298 TATTTTCAAAAAATT 10.8 dppA 40 ATTATTCTGAAAATT 10.8 lysS 41 TATTTTCAAAAAATT 10.8 dppP 46 AATTTTCTGACAATA 10.7 yeaG 403 ATTTTTCTGAAAATA 10.7 gerCB 234 ATTTTTCAGAAAATA 10.7 yqcE 87 GTTTTTCTGAAAATT 10.7 menD 654 AATTTTCAGAAGAAT 10.7 mfd 397 AATTTTCTAAAAAGT 10.6 dppP 114 AATTTTCAGAAAACA 10.6 yfhC 68 TATTTTCAAAAAAAT 10.6 arsC 642 CATCTTCAGAAAATT 10.6 amtB 46 AATATTCAGAAAATA 10.6 purL 1238 AATTTTCAAAAAACT 10.6 yojB 187 AATTTTCAGAAAAGA 10.6 ilvD 71 AATGTTCTGACAAAT 10.6 ysbD 34 AATTTTTTGAAAAAT 10.6 ysdE 126 AATTTTTTGAAAAAT 10.6 ybaB 103 ATTTTACAGAAAATT 10.5

a) Distance of the 3’-end of the CodY-box relative to the position of the initiating codon of the downstream ORF. b) Arbitrary score of similarity of the element with the CodY-box consensus.

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Supplementary TABLE 2. Occurrence of CodY-box derivates in the genome of L. lactis IL1403

Gene Positiona Sequence Scoreb

yghD 99 AATTTTCTGAAAATT 11,8 optS 227 AATTTTCAGAAAATT 11,8 feoA 85 AATTTTCTGAAAAAT 11,6 codY 86 AATTTTCTGACAATT 11,4 birA2 156 ATTTTTCTGAAAATT 11,3 yrbI 524 TATTTTCTGAAAAAT 11,3 dinG 710 TATTTTCTGAAAAAT 11,3 thrA 55 AATTTTCAGATAATT 11,3 ygjD 99 ATTTTTCAGAAAATT 11,3 serC 44 AATTATCAGAAAATT 11,3 metA 209 AATTTTCCGAAAAAT 11,2 gltA 51 AATTTTCAGAAAATA 11,2 amtB 47 TATTTTCTGACAATT 11,1 yeiD 243 AATTGTCTGAAAAAT 11,1 pi249 186 TATCTTCTGAAAATT 10,9 ygcC 397 AATTTTCAGAAAAAA 10,9 yeaG 403 TATTTTCTGAAAAGT 10,9 ctrA 60 AATTGTCAGACAATT 10,9 mfd 396 AATTTTCTAAAAAAT 10,9 ywdD 940 AATGGTCAGAAAATT 10,8 noxD 681 AATGGTCAGAAAATT 10,8 pi303 242 ATTTTTCAGATAATT 10,8 ynaD 110 AATTATCGGAAAAAT 10,8 yjiF 199 AATTTTATGAAAATT 10,8 lysS 40 TATTTTCAAAAAATT 10,8 optA 114 TGTTTTCTGAAAATT 10,8 optS 40 AATTTTCAGAATAAT 10,8 optA 108 ATTTTTCTGATAATT 10,8 yceD 309 TTTTTTCTGAAAAAT 10,8 yrbA 112 TATTTACTGAAAATT 10,7 arcB 635 AATTTGCTGAAAAAT 10,7 ileS 170 ATTTTTCTAAAAATT 10,7 ysbD 354 ATTTTTCAAAAAATT 10,7 pepF 133 AATTTTCAGCAAAAT 10,7 pepXP 45 TATTTACTGAAAATT 10,7

a) Distance of the 3’-end of the CodY-box relative to the position of the initiating codon of the downstream ORF. b) Arbitrary score of similarity of the element with the CodY-box consensus.

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Supplementary TABLE 3. Occurrence of CodY-box derivates in the genome of S. pneumonia R6

Gene Positiona Sequence Scoreb

ilvD 69 AATTTTCAGAAAATT 11,8 ilvE 73 AATTTTCTGAAAATT 11,8 rgg 39 AATTTTCTGAAAAAT 11,6 thrC 42 AATTTTCTGAAAAAT 11,6 IS1381 31 AATTTTCTGAAAAAT 11,6 leuA 34 TATTTTCTGAAAATT 11,5 gapN 55 TATTTTCTGAAAATT 11,5 amiA 72 AATATTCTGAAAATT 11,3 codY 55 AATTATCTGAAAATT 11,3 livJ 46 AATTTTCTGATAATT 11,3 spr0332 59 AATTTTCGGAAAAAT 11,3 asD 16 AATTTTCTAAAAATT 11,2 zwF 79 AATTTTCCGAAAAAT 11,2 gdhA 79 AATTTTCTAAAAATT 11,2 ppmA 53 GATTTTCAGAAAAAT 10,9 hom 8 AATTTTGTGAAAATT 10,8 pnp 128 ATTCTTCAGAAAATT 10,8 mtlD 154 ATTATTCAGAAAATT 10,8 spr0157 18 AATTTTCAGAATAAT 10,8 spr0806 40 CATTATCAGAAAATT 10,7 pepA 221 TATTTTCTGTAAATT 10,6 spr1436 40 TATTATCTGACAATT 10,6 spr1115 209 AAATTTCAGAAAAAT 10,6 gldA 49 AATCGTCAGAAAAAT 10,6 aqpZ 74 GATTTTCAAAAAATT 10,5 thrS 128 TATTTTCTGAAAGTT 10,5 spr0685 23 ATTTTTCAGAAAATC 10,5

a) Distance of the 3’-end of the CodY-box relative to the position of the initiating codon of the downstream ORF. b) Arbitrary score of similarity of the element with the CodY-box consensus.

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Supplementary TABLE 4. Occurrence of CodY-box derivates in the genome of B. subtilis 168

Gene Positiona Sequence Scoreb

yvbF 221 AATTTTCTGAAAAGT 11,2 glnQ 45 AATTTTCAGAAAAGT 11,2 ytkC 66 ATTTTTCTGAAAAAT 11,1 ytnA 15 AATATTCAGAAAAAT 11,1 phoA 141 ATTTTTCTGAAAAAT 11,1 yerL 157 AATATTCAGAAAAAT 11,1 yufN 114 TATTATCAGAAAATT 11,0 yuiA 21 TATTATCAGAAAATT 11,0 spoIIQ 27 TATTTTCAGAAAAGT 10,9 opuBA 49 ATTTTTCAGACAATT 10,9 lipB 69 AATTTTCAGAAAAAA 10,9 yocS 77 AATTTTCTGAATAAT 10,8 ykrQ 75 AATTTTCTGAAATTT 10,8 ydjJ 242 AATTTTCAGAAATTT 10,8 ykwB 36 TATTTACTGAAAATT 10,7 yfmB 79 ATTTTTCTGAAAATA 10,7 braB 44 TATTATCTGACAATT 10,6 citB 57 AATTTTCTCACAATT 10,6 ynzD 120 TATTTTCAGAAAAAA 10,6 ileS 17 TATTTTCTGAAAAAA 10,6 nasD 106 AATTTTATGAAAAAT 10,6 yxiE 84 AGTTTTCAAAAAATT 10,5 yurP 85 TATTTTCTGAAATTT 10,5 yurF 104 CATTTTCTGACAAAT 10,5 ykuW 119 CATTTTCAGAAAATA 10,5 ybgA 100 TAATTTCTGAAAATT 10,5

a) Distance of the 3’-end of the CodY-box relative to the position of the initiating codon of the downstream ORF. b) Arbitrary score of similarity of the element with the CodY-box consensus.

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Supplementary TABLE 5. Occurrence of CodY-box derivates in the upstream regions of genes identified by Molle et al. (2003) as being direct targets of CodY of B. subtilis 168

Gene Positiona Sequence Scoreb

yufN 114 TATTATCAGAAAATT 11.0 citB 57 AATTTTCTCACAATT 10.6 yurP 85 AAATTTCAGAAAATA 10.2 yhdG 166 ATTTTTCTAACAATT 10.2 gggA 184 TTTTTGCTGAAAATT 10.1 yxbC 70 AATCCTCTGATAATT 10.1 yhjC 144 TAATTTCAGACAATT 10.1 ybgE 103 AAATTTCAGAATATT 10.1 ilvD 48 AATAAACTGAAAATT 9.9ispA 132 AATCTTCAAAATATT 9.8appD 83 AATTTTTCGATAATT 9.8yoaD 8 TTTTTTATGAAAAAT 9.8ykaA 161 ATTTATCAAAAAAGT 9.6comK 15 ATTTTGCAGAAAAAG 9.4citB 135 ACTTATGAGAAAAAT 9.4yhdG 43 TGAATTCAGAAAATT 9.3guaB 13 TCTTTTCGGCAAAAT 9.3acsA 63 TATATTTTAAAAATT 9.3ybgE 22 AATATTTAAACAATT 9.2yoaD 187 TTCATTCTGAAAATT 9.1hutP 11 AAAATTCTGATAACT 9.1guaB 10 CTTCTTTTGAAAATT 9.1ureA 47 AATTTGCGGAACAGT 9.1dppA 28 ATTTGTTAGAATATT 9.1yusC 19 ACTATTCTAAGAAAT 9.0ycgM 91 AATAATCAGAATCTT 9.0ilvD 117 AATTGTCAAAATAAA 9.0rocA 73 TTTTTTCAGCAAAAG 9.0

a) Distance of the 3’-end of the CodY-box relative to the position of the initiating codon of the downstream ORF. b) Arbitrary score of similarity of the element with the CodY-box consensus.

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and Oscar P. KuipersChris D. den Hengst, Sacha A. F. T. van Hijum, Jan M. W. Geurts, Arjen Nauta, Jan Kok

elementThe lactococcus lactis CodY regulon: Identifcation of a conserved cis-regulatory

published online July 21, 2005J. Biol. Chem. 

  10.1074/jbc.M502349200Access the most updated version of this article at doi:

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Supplemental material:

  http://www.jbc.org/content/suppl/2005/08/02/M502349200.DC1

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